I wanted to love Obsidian for Android because it's Canadian but I don't, not yet. It made me think way too much to use it to a point of frustration. The UI is awkward on a smartphone as it's trying to replicate the desktop UI. Initial loading is quite slow. It has markdown support, outlining, and the extensibility is incredible with themes and plugins supported by a large and loyal community of Developers / Scripters.
I also posted a review of their other app, see Dynalist v1.4.15 scores 8/10. Soon I will be publishing a post on how to use Obsidian with Nextcloud on Android, it's painful but doable so be sure to subscribe to get notified.